The present invention relates generally to an imaging module and an imaging reader for, and a method of, variably illuminating targets to be read by image capture over a range of working distances.
Solid-state imaging systems or imaging readers have been used, in both handheld and/or hands-free modes of operation, to electro-optically read targets, such as one- and two-dimensional bar code symbol targets, and/or non-symbol targets, such as documents. A handheld imaging reader includes a housing having a handle held by an operator, and an imaging module, also known as a scan engine, supported by the housing and aimed by the operator at a target during reading. The imaging module includes an imaging assembly having a solid-state imager or imaging sensor with an imaging array of photocells or light sensors, which correspond to image elements or pixels in an imaging field of view of the imager, and an imaging lens assembly for capturing return light scattered and/or reflected from the target being imaged, and for projecting the return light onto the array to initiate capture of an image of the target. Such an imager may include a one- or two-dimensional charge coupled device (CCD) or a complementary metal oxide semiconductor (CMOS) device and associated circuits for producing and processing electronic signals corresponding to a one- or two-dimensional array of pixel data over the imaging field of view. In order to increase the amount of the return light captured by the array, for example, in dimly lit environments, the imaging module generally also includes an illuminating light assembly for illuminating the target with illumination light in an illumination pattern for reflection and scattering from the target.
In some applications, for example, in warehouses, it is sometimes necessary for the same reader to read not only far-out targets, e.g., on products located on high overhead shelves, which are located at a far-out range of working distances on the order of thirty to fifty feet away from the reader, but also close-in targets, e.g., on products located at floor level or close to the operator, which are located at a close-in range of working distances on the order of less than two feet away from the reader. The reader illuminates the far-out targets by emitting an intense, bright illumination light in order to enable such targets to be reliably imaged and read. However, when the same bright illumination light illuminates the close-in targets, the imaging array of photocells becomes blinded, and such targets are not readily read. If an aiming assembly is employed to locate a close-in target by directing an aiming pattern thereon, then the bright illumination light may even wash out the aiming pattern and can cause reading performance to deteriorate. In addition, the bright illumination light increases electrical power consumption, and wastes energy. Moreover, the bright illumination light can be bothersome and annoying to the operator and to any nearby passersby.
Accordingly, there is a need to reduce the electrical power consumption of the imaging module and of the overall reader, to prevent the aiming pattern from being washed out, to avoid blinding of the imaging array, to avoid annoying the operator and any passersby, and to reliably read both far-out targets and close-in targets with the same reader.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions and locations of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.
The system and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.